January 2003 arXiv papers — page 12

Laurent Buse, Marc Chardin

In this paper we describe an algorithm for implicitizing rational hypersurfaces in case there exists at most a finite number of base points. It is based on a technique exposed in math.AG/0210096, where implicit equations are obtained as determinants of certain graded parts of a so-called approximation complex. We detail and improve this method by providing a

Boris Tsirelson

Linear functions of many independent random variables lead to classical noises (white, Poisson, and their combinations) in the scaling limit. Some singular stochastic flows and some models of oriented percolation involve very nonlinear functions and lead to nonclassical noises. Two examples are examined, Warren's `noise made by a Poisson snake' and t

Hovhannes M. Khudaverdian, Theodore Voronov

We solve the following problem: to describe in geometric terms all differential operators of the second order with a given principal symbol. Initially the operators act on scalar functions. Operator pencils acting on densities of arbitrary weights appear naturally in the course of study. We show that for the algebra of densities it is possible to establish a

Mark Holland, Stefano Luzzatto

We introduce a new technique for proving the classical Stable Manifold theorem for hyperbolic fixed points. This method is much more geometrical than the standard approaches which rely on abstract fixed point theorems. It is based on the convergence of a canonical sequence of ``finite time local stable manifolds'' which are related to the dynamics of

Dmitri Piontkovski

We study associative graded algebras which have a ``complete flag'' of cyclic modules with linear free resolutions, i.e., algebras over which there is a cyclic Koszul module with every admissible number of relations (from zero up to the number of generators of the algebra). Commutative algebras with the same property has been studied in several paper

Mark Hovey, Neil Strickland

We show that, if E is a Landweber exact ring spectrum, then the category of E_*E-comodules is equivalent to the localization of the category of BP_*BP-comodules with respect to the hereditary torsion theory of v_n-torsion comodules, where n is the height of E. In particular, the category of E(n)_*E(n)-comodules is equivalent to the category of (v_n^{-1}BP)_*

Mark Hovey, Neil Strickland

In a previous paper, the authors showed that the category of E(n)_*E(n)-comodules is a localization of the category of BP_*BP-comodules. In this paper, we study the resulting localization functor L_n on the category of BP_*BP-comodules. It is an algebraic analogue of the usual topological localization L_n. It is left exact, so has right derived functors L_n^

Mark Hovey

This paper begins with an exposition of the author's research on the category of BP_*BP-comodules, much of which is joint with Neil Strickland. The main result of that work is that the category of E(n)_*E(n)-comodules is equivalent to a localization of the category of BP_*BP-comodules (the localization is L_n, analogous to the topological L_n). The main

Mark Hovey

Given a good homology theory E and a topological space X, the E-homology of X is not just an E_{*}-module but also a comodule over the Hopf algebroid (E_{*}, E_{*}E). We establish a framework for studying the homological algebra of comodules over a well-behaved Hopf algebroid (A, Gamma). That is, we construct the derived category Stable(Gamma) of (A, Gamma)

Paul-Andi Nagy

We study special almost Kaehler manifolds whose curvature tensor satisfies the second curvature condition of Gray. It is shown that for such manifolds, the torsion of the first canonical Hermitian is parallel. This enables us to show that every AK_2-manifold has parallel torsion. Some applications of this result, concerning the existence of orthogonal almost

A. Calabri, C. Ciliberto, F. Flamini, R. Miranda

In this paper we study some properties of degenerations of surfaces whose general fibre is a smooth projective surface and whose central fibre is a reduced, connected surface $X \subset IP^r$, $r \geq 3$, which is assumed to be a union of smooth projective surfaces, in particular of planes. Our original motivation has been a series of papers of G. Zappa whic

Craig D. Hodgson, Steven P. Kerckhoff

This paper gives an exposition of the authors' harmonic deformation theory for 3-dimensional hyperbolic cone-manifolds. We discuss topological applications to hyperbolic Dehn surgery as well as recent applications to Kleinian group theory. A central idea is that local rigidity results (for deformations fixing cone angles) can be turned into effective con

Christian Haase, Ilia Zharkov

This paper is a continuation of our paper math.AG/0205321 where we have built a combinatorial model for the torus fibrations of Calabi-Yau toric hypersurfaces. This part addresses the connection between the model torus fibration and the complex and Kähler geometry of the hypersurfaces.

Alexander Borichev, Fedor Nazarov, Mikhail Sodin

Let F be a class of functions with the uniqueness property: if a function f in F vanishes on a set of positive measure, then f is the zero function. In many instances, we would like to have a quantitative version of this property, e.g. a lower bound for |f| outside a small exceptional set. Such estimates are well-known and useful for polynomials, complex- an

Elisabeth Remm

In this paper we study some affine structures on nilpotent Lie algebras endowed with a contact form. These affine structures are constructed from an affine structure on a symplectic Lie algebra by a central extension.

Elisabeth Remm

In this note we prove that every non characteristically filiform Lie algebra is endowed with an affine structure.

Stephen Pinsky

Recently it has been demonstrated by Dienes and Mafi, that the physics of toroidal compactified models of extra dimensions can depend on the shape angle of the torus. Toroidal compactification has also recently been used as a regulator for numerical solutions of supersymmetric fields theories in 2+1 dimensions. The question is; does the shape angle of the to

I. Dadic, L. Jonke, S. Meljanac

A generalized harmonic oscillator on noncommutative spaces is considered. Dynamical symmetries and physical equivalence of noncommutative systems with the same energy spectrum are investigated and discussed. General solutions of three-dimensional noncommutative harmonic oscillator are found and classified according to dynamical symmetries. We have found cond

E. T. Akhmedov

In this note we establish the explicit relation between correlation functions in ${\cal N} = 4$ SUSY Yang--Mills theory on $S^3\times R$ in a double scaling limit and scattering amplitudes of the String Theory on the pp-wave background. The relation is found for two-- and three--point correlation functions in these theories. As a by product we formulate a di

A. Ivanov, R. Kirschner

The end-point contributions in the quark longitudinal momentum fraction of the virtual photon ($γ^*$) to vector meson ($V$) impact factor to the diffractive electroproduction amplitude can be factorized in terms of a generalized parton evolution of the target parton distribution. The result is used to model the helicity amplitudes $γ^* p \to V p$ in terms of

E. A. Kuraev, Z. K. Silagadze

The aim of this paper is twofold: to provide a rather detailed and self-contained introduction into the physics of the Disoriented Chiral Condensate (DCC) for the photon (and linear) collider community, and to indicate that such physics can be searched and studied at photon colliders. Some side tracks are also occasionally followed during the exposition, if

R. B. Nevzorov, M. A. Trusov

The simplest extension of the MSSM that does not contradict LEP II experimental bound on the lightest Higgs boson mass at $\tanβ\sim 1$ is the modified Next-to-Minimal Supersymmetric Standard Model (MNSSM). We investigate the renormalization of Yukawa couplings and soft SUSY breaking terms in this model. The possibility of $b$-quark and $τ$-lepton Yukawa cou

A. Del Fabbro, D. Treleani

The large parton flux at high energy gives rise to events where different pairs of partons interact contemporarily with large momentum exchange. A main effect of multiple parton interactions is to generate events with many jets at relatively large transverse momenta. The large value of the heavy quarks production cross section may however give also rise a si

F. Schrempp, A. Utermann

We briefly report on the contribution of QCD-instantons to the phenomenon of saturation in deep-inelastic scattering (DIS) at small Bjorken-x. The explicitly known instanton gauge field serves as a concrete realization of an underlying non-perturbative saturation mechanism associated with strong classical fields. Two independent strategies were pursued, with

R. Martinez, N. Poveda, J. -Alexis Rodriguez

Anomalous moments of the top quark arises from one loop corrections to the vertices $\bar t t g$ and $\bar t t γ$. We study these anomalous couplings in different frameworks: effective theories, Standard Model and 2HDM. We use available experimental results in order to get bounds on these anomalous couplings.

A. Del Fabbro, D. Treleani

A sizable rate of events, with several pairs of $b$-quarks produced contemporarily by multiple parton interactions, may be expected at very high energies as a consequence of the large parton luminosities. The production rates are further enhanced in hadron-nucleus reactions, which may represent a convenient tool to study the phenomenon. We compare the differ

A. Giovannini, R. Ugoccioni

Continuing previous work on forward-backward multiplicity correlation properties in proton-proton collisions in the framework of the weighted superposition model of two components (each one described by a negative binomial multiplicity distribution) with the addition of the leakage parameter which controls clan spreading from one hemisphere to the opposite o

Shingo Kiyoura, Shinya Kanemura, Kosuke Odagiri, Yasuhiro Okada

We report the important topics in ACFA report as well as the recent progress in the ACFA Higgs working group.

Z. Chacko, Eduardo Ponton

We consider five dimensional supersymmetric warped scenarios in which the Standard Model quark and lepton fields are localized on the ultraviolet brane, while the Standard Model gauge fields propagate in the bulk. Supersymmetry is assumed to be broken on the infrared brane. The relative sizes of supersymmetry breaking effects are found to depend on the hiera

Thomas R. Hemmert, Massimiliano Procura, Wolfram Weise

We report on recent work about the study of quark mass dependence of nucleon magnetic moments and axial-vector coupling constant. We examine the feasibility of chiral effective field theory methods for the extrapolation of lattice QCD data obtained at relative large pion masses down to the physical values.

Donato Bini, Christian Cherubini, Robert T. Jantzen, Bahram Mashhoon

A single master equation is given describing spin $s\le2$ test fields that are gauge- and tetrad-invariant perturbations of the Kerr-Taub-NUT spacetime representing a source with mass $M$, gravitomagnetic monopole moment $-\ell$ and gravitomagnetic dipole moment (angular momentum) per unit mass $a$. This equation can be separated into its radial and angular

A. A. Sousa, J. W. Maluf

We apply the Hamiltonian formulation of teleparallel theories of gravity in 2+1 dimensions to a circularly symmetric geometry. We find a family of one-parameter black hole solutions. The BTZ solution fixes the unique free parameter of the theory. The resulting field equations coincide with the teleparallel equivalent of Einstein's three-dimensional equat

R. Aldrovandi, P. B. Barros, J. G. Pereira

A gravitational field can be seen as the anholonomy of the tetrad fields. This is more explicit in the teleparallel approach, in which the gravitational field-strength is the torsion of the ensuing Weitzenboeck connection. In a tetrad frame, that torsion is just the anholonomy of that frame. The infinitely many tetrad fields taking the Lorentz metric into a

Sascha Husa, Christiane Lechner

We discuss the application of computer algebra to problems commonly arising in numerical relativity, such as the derivation of 3+1-splits, manipulation of evolution equations and automatic code generation. Particular emphasis is put on working with abstract index tensor quantities as much as possible.

L. C. Garcia de Andrade

A non-minimal photon-torsion axial coupling in the quantum electrodynamics (QED) framework is considered. The geometrical optics in Riemannian-Cartan spacetime is considering and a plane wave expansion of the electromagnetic vector potential is considered leading to a set of the equations for the ray congruence. Since we are interested mainly on the torsion

Justin Corvino, Richard M. Schoen

Given asymptotically flat initial data on M^3 for the vacuum Einstein field equation, and given a bounded domain in M, we construct solutions of the vacuum constraint equations which agree with the original data inside the given domain, and are identical to that of a suitable Kerr slice (or identical to a member of some other admissible family of solutions)

P. Dusart, G. Letourneux, O. Vivolo

We explain how a differential fault analysis (DFA) works on AES 128, 192 or 256 bits.

Daniel A. Spielman, Shang-Hua Teng

We perform a smoothed analysis of the termination phase of an interior-point method. By combining this analysis with the smoothed analysis of Renegar's interior-point algorithm by Dunagan, Spielman and Teng, we show that the smoothed complexity of an interior-point algorithm for linear programming is $O (m^{3} \log (m/σ))$. In contrast, the best known bo

Srinidhi Varadarajan, Naren Ramakrishnan

Grid infrastructures and computing environments have progressed significantly in the past few years. The vision of truly seamless Grid usage relies on runtime systems support that is cognizant of the operational issues underlying grid computations and, at the same time, is flexible enough to accommodate diverse application scenarios. This paper addresses the

Qing-feng Sun, Hong Guo, Jian Wang

We theoretically predict that a pure steady state spin-current without charge-current can induce an electric field. A formula for the induced electric field is derived and we investigate its characteristics. Conversely, a moving spin is affected by an external electric field and we present a formula for the interaction energy.

Y. Saito, A. Koga, N. Kawakami

We study the effects of hole doping on the two-dimensional Heisenberg-Kondo model around the quantum critical point, where the spin liquid phase (Kondo insulator) and the magnetically ordered phase are separated via a second-order phase transition. By means of the self-consistent Born approximation within the bond operator formalism as well as the standard s

Csaba Foldy, Zoltan Somogyvari, Peter Erdi

In this paper a hierarchical extension of the Minority Game is defined and studied. Numerical simulations show a special type of emergent global behavior between separated parts of the hierarchical structure, connected only through a normalized mean field quantity.

A. Benyoussef, H. Chakib, H. Ez-Zahraouy

By the use of computer simulations we investigate, in the cellular automaton of two-dimensional traffic flow, the anisotropic effect of the probabilities of the change of the move directions of cars, from up to right ($p_{ur}$) and from right to up ($p_{ru}$), on the dynamical jamming transition and velocities under the periodic boundary conditions in one ha

Scott Drewes, Daniel P. Arovas, Scot Renn

The Ueda-Guinea model of a dissipative tunnel junction is investigated. This model accounts for final state effects associated with single-electron tunneling. A quantum phase transition emerges, marking a boundary between insulating (Coulomb blockade) and conducting phases. The system is analyzed by large-N techniques, self-consistent harmonic approximation,

L. M. Sander, C. P. Warren, I. M. Sokolov

Spatial models for spread of an epidemic may be mapped onto bond percolation. We point out that with disorder in the strength of contacts between individuals patchiness in the spread of the epidemic is very likely, and the criterion for epidemic outbreak depends strongly on the disorder because the critical region of the corresponding percolation model is br

S. A. Tarasenko, E. L. Ivchenko, V. V. Bel'kov, S. D. Ganichev

It is shown that absorption of circularly polarized infrared radiation due to intraband (Drude-like) transitions in n-type bulk semiconductors and due to intra-subband or inter-subband transitions in quantum well (QW) structures results in a monopolar spin orientation of free electrons. Spin polarization in zinc-blende-structure based QWs is demonstrated by

K. Michielsen, J. S. Kole

We calculate the photonic band gap of triply periodic bicontinuous cubic structures and of tubular structures constructed from the skeletal graphs of triply periodic minimal surfaces. The effect of the symmetry and topology of the periodic dielectric structures on the existence and the characteristics of the gaps is discussed. We find that the C(I2-Y**) stru

E. Valencia-Morales, N. J. Galeano-Alvarez, J. Vega-Leyva, C. E. Villar

Often a number of precipitation processes in steels and alloys occur simultaneously (they have the same origin in time) albeit at different rates. Consequently, isothermic transformations are accompanied, in this case, by the occurrence of second processes of precipitation that influence the changes of the macroscopic parameter chosen for the kinetic study w

S. D. Ganichev, E. L. Ivchenko, V. V. Bel'kov, S. A. Tarasenko

It is shown that a homogeneous non-equlibrium spin-polarization in semiconductor heterostructures results in an electric current. The microscopic origin of the effect is an inherent asymmetry of spin-flip scattering in systems with lifted spin degeneracy caused by k-linear terms in the Hamiltonian.

V. V. Bel'kov, S. D. Ganichev, Petra Schneider, D. Schowalter

A detailed study of the circular photogalvanic effect (CPGE) in SiGe structures is presented. It is shown that the CPGE becomes possible due to the built-in asymmetry of quantum wells (QWs) in compositionally stepped samples and in asymmetrically doped structures. The photocurrent arises due to optical spin orientation of free carriers in QWs with spin split

S. A. Tarasenko, E. L. Ivchenko, V. V. Bel'kov, S. D. Ganichev

It is shown that absorption of circularly polarized infrared radiation achieved by inter-subband and intra-subband (Drude-like) transitions results in a monopolar spin orientation of free carriers. The monopolar spin polarization in zinc-blende-based quantum wells (QWs) is demonstrated by the observation of the spin-galvanic and circular photogalvanic effect

Robert Koelbl, Dirk Helbing

We show that energy concepts can contribute to the understanding of human travel behaviour. First, the average travel times for different modes of transportation are inversely proportional to the energy consumption rates measured for the respective physical activities. Second, when daily travel-time distributions by different modes of transport such as walki

Guotai Tan, S. Dai, P. Duan, H. B. Lu

The electronic structure of La0.8Sr0..2MnO3/SrTiO thin film, which was prepared by Laser MBE, was studied by X-ray photoemission spectra (XPS) in the temperature interval of 300 to 1000 K. Experimental results showed that the electronic state of the thin film underwent a discontinuous variation between 350 K and 450 K, indicating that the metal-semiconductor

Guotai Tan, P. Duan, S. Y. Dai, Y. L. Zhou

In this study we report the structure, magnetic and electrical transport properties of pervoskite oxide La$sub{0.9}Tesub{0.1}MnOsub{3}$. This is a novel material with the space group R-3c, which shows the spin-glass-like feature at low temperature and has a good colossal magnetoresistance behavior. The magnetoresistance ratio is about 51% at 200 K in a field

V. Blavatska, C. von Ferber, Yu. Holovatch

We investigate the critical properties of d-dimensional magnetic systems with quenched extended defects, correlated in $ε_d$ dimensions (which can be considered as the dimensionality of the defects) and randomly distributed in the remaining $d-ε_d$ dimensions; both in the case of fixed dimension d=3 and when the space dimension continuously changes from the

M. Decroux, L. Antognazza, S. Reymond, W. Paul

We present experimental results on the behaviour of a superconducting YBCO/Au meander of length L submitted to short circuit tests with constant voltage pulses. The meander, at the beginning of the short-circuit, is divided in two regions; one, with a length L1 proportional to the applied voltage, which first switches into a highly dissipative state (HDS) wh

Balázs Dóra, Kazumi Maki, Attila Virosztek

We compute the optical conductivity of 2D f-wave superconductors and also of the multigap model proposed recently by Zhitomirsky and Rice at T=0K in the Born limit. The presence of interband impurity scattering was found to play an important role: the contributions from the two bands mix up, and new structures are seen in the tunneling density of states and

Keshav N. Shrivastava

It is shown that even number of flux quanta are not attached to one electron. The magnetic flux is not detached from the currents and the E and H separation does not occur in the quantum Hall effect, where E is the electric vector and H is the magnetic vector of the electro- magnetic field. We show how a sequence can agree with the experimental data and be w

R. G. Dias, J. A. Silva

We present a study of the temperature-magnetic field phase diagram of homogeneous and inhomogeneous superconductivity in the case of a quasi-two-dimensional superconductor with an extended saddle point in the energy dispersion under a parallel magnetic field. At low temperature, a huge metastability region appears, limited above by a steep superheating criti

G. De Fabritiis, P. V. Coveney

In this paper, we review the computational aspects of a multiscale dissipative particle dynamics model for complex fluid simulations based on the feature-rich geometry of the Voronoi tessellation. The geometrical features of the model are critical since the mesh is directly connected to the physics by the interpretation of the Voronoi volumes of the tessella

Y. Joly, S. Grenier, J. E. Lorenzo

We show that in mixed-valence 3d transition metal oxides undergoing a structural transition, the low temperature phase results from an effective ordering of the charge. This arrangement and the quantitative evaluation of the atomic charges are determined by using resonant x-ray scattering experiments further analyzed with the help of ab initio calculations o

S. H. Naqib, J. R. Cooper, J. L. Tallon

The effects of planar hole concentration, p, on the resistivity, r(T), of sintered Y1-xCaxBa2(Cu1-yZny)3O7-d samples were investigated over a wide range of Ca, Zn, and oxygen contents. Zn was used to suppress superconductivity and this enabled us to extract the characteristic pseudogap temperature, T*(p), from r(T,p) data below Tco(p) [ = Tc (y = 0)]. We hav

Jonathan P. K. Doye

Putative global minima have been located for clusters interacting with an aluminium glue potential for N<190. Virtually all the clusters have polytetrahedral structures, which for larger sizes involve an ordered array of disclinations that are similar to those in the Z, H and sigma Frank-Kasper phases. Comparisons of sequences of larger clusters suggest that

R. Koch, O. Waldmann, P. Mueller, U. Reimann

We investigated the magnetic properties of two isostructural Ni(II) metal complexes [Ni4Lb8] and [Ni4Lc8]. In each molecule the four Ni(II) centers form almost perfect regular squares. Magnetic coupling and anisotropy of single crystals were examined by magnetization measurements and in particular by high-field torque magnetometry at low temperatures. The da

Morten Kloster, Chao Tang

We study theoretically the in vitro evolution of a DNA sequence by binding to a transcription factor. Using a simple model of protein-DNA binding and available binding constants for the Mnt protein, we perform large-scale, realistic simulations of evolution starting from a single DNA sequence. We identify different parameter regimes characterized by distinct

M. R. Dudek, S. Cebrat, M. Kowalczuk, P. Mackiewicz

The coding sequence in DNA molecule is considered as a message to be transferred to receiver, the proteins, through a noisy information channel and each nucleotide is assigned a respective information weight. With the help of the nucleotide substitution matrix we estimated the lower bound of the amount of information carried out by nucleotides which is not s

Takenori Fujii, Ichiro Terasaki

A parent insulator of the Bi-based high-$T_c$ superconductor Bi$_2$Sr$_{2-x}$La$_x$CaCu$_2$O$_{8+δ}$ was successfully grown by a traveling solvent floating zone method. The in-plane resistivity $ρ_{ab}$ shows metallic behavior ($dρ_{ab}/dT >$ 0) near room temperature, although the magnitude of the resistivity is far above the Mott limit for metallic conducti

T. Saso

Thermoelectric effects in Kondo insulators are attracting interests because of the emerging possibility of developping better thermoelectric materials for a portable refrigerator without liquid coolant. In this article, the theory of thermoelectric effects are reinvestigated for insulators or semiconductors at low temperatures. It is found that the famous re

B. Basu, S. Dhar, P. Bandyopadhyay

We have discussed here the polarization of quantum Hall states in the framework of the hierarchical analysis of IQHE and FQHE in terms of Berry phase. It is observed that we have fully polarized states for the filling factor $ν=1$ as well as $ν=\frac{1}{2m+1}$, $m$ being an integer. However, for $ν=p$ as well as $ν=\frac{p}{q}$, with $p>1$ and odd, $q$ odd w

Z. Y. Liu, H. H. Wen, T. Xiang, Seiki Komiya

Low temperature specific heat has been measured for an overdoped $La_{2-x}Sr_xCuO_4$ (x = 0.22) single crystal. The quasiparticle density of states (DOS) in the mixed state is found to deviate from the predicted scaling law $C_{vol}=Hf(T/H^{1/2})$. However, this scaling behavior is nicely reconciled if one considers the normal core region ($ξ\approx$ 21$Å$)

Masaki Sasai, Peter G. Wolynes

Gene expression has a stochastic component owing to the single molecule nature of the gene and the small number of copies of individual DNA binding proteins in the cell. We show how the statistics of such systems can be mapped on to quantum many body problems. The dynamics of a single gene switch resembles the spin boson model of a two site polaron or an ele

B. J. Powell, James F. Annett, B. L. Gyorffy

We propose a simple picture for the occurrence of superconductivity and the pressure dependence of the superconducting critical temperature, T_{SC}, in ZrZn_2. According to our hypothesis the pairing potential is independent of pressure, but the exchange splitting, E_{xc}, leads to a pressure dependence in the (spin dependent) density of states at the Fermi

A. V. Nikolaev, K. H. Michel

We discuss the triple-$\vec{q}^X$ structures for the ordered cubic phase of NpO$_2$, which are $Pn{\bar 3}m$ and $Pa{\bar 3}$. A special care should be taken to discriminate between these two cases. We analyze the relevant structure-factor amplitudes and the effect of domains on resonant X-ray scattering experiments. We formulate the technique of multipole e

Abhishek Dhar

We study heat conduction in quantum disordered harmonic chains connected to general heat reservoirs which are modeled as infinite collection of oscillators. Formal exact expressions for the thermal current are obtained and it is shown that, in some special cases, they reduce to Landauer-like forms. The asymptotic system size dependence of the current is anal

M. J. Konstantinović, J. van den Brink, Z. V. Popović, V. V. Moshchalkov

We study with the Raman scattering technique two types of phase transitions in the pyroxene compounds NaMSi$_2$O$_6$ (with M=Ti, V, and Cr). In the quasi one-dimensional S=1/2 system NaTiSi$_2$O$_6$ we observe anomalous high-temperature phonon broadening and large changes of the phonon energies and line-widths across the phase transition at 210 K. The phonon

Lisa A. Crause, Warrick A. Lawson, David Kilkenny, Francois van Wyk

The unusual eruptive variable discovered in Monoceros in 2002 January underwent dramatic photometric and spectroscopic changes in the months prior to its 2002 June-August conjunction with the Sun. Optical and infrared (IR) photometry obtained at the South African Astronomical Observatory (SAAO) between 2002 January and June (JD 2452280-440) is presented here

Claudia Maraston

This review deals with stellar population models computed by means of the evolutionary synthesis technique that was pioneered by Beatrice Tinsley roughly three decades ago. The focus is on the simplest models, the so called Simple Stellar Populations, that describe instantaneous generations of single stars with the same chemical composition and age. The deve

Ann Marie Cody, Robert Braun

We present 92cm observations of the high-redshift galaxy B2 0902+343 (z=3.40) with the Westerbork Synthesis Radio Telescope (WSRT). Twenty-one cm HI is detected in absorption, at a depth of 15.9 mJy (=~6σ) and rest frame velocity width 120 km/s. We also report a null detection of OH emission or absorption at the 1665/1667 MHz rest-frame transitions. Based on

K. Kohno, B. Vila-Vilaro, S. Sakamoto, R. Kawabe

Aperture synthesis observations of CO(J=1-0) emission and near-infrared broad-band photometry of the non-barred Seyfert galaxy NGC 5033 (D = 18.7 Mpc) were performed. Our 3&#34;.9 x 3&#34;.6 resolution CO observations reveal a perturbed distribution and the kinematics of molecular gas in the center of NGC 5033; we find the characteristic gaseous features tha

Wayne Hu

Cluster number counts offer sensitive probes of the dark energy if and only if the_evolution_ of the cluster mass versus observable relation(s) is well calibrated. We investigate the potential for internal calibration by demanding consistency in the counts as a function of the observable. In the context of a constant dark energy equation of state, known init

S. N. Shore, G. Schwarz, H. E. Bond, R. A. Downes

We present a multiwavelength study of the ONeMg Galactic nova V382 Velorum 1999 using HST/STIS and FUSE ultraviolet spectra and comparisons with published groundbased optical spectra. We find a close match to the basic phenomenology of another well-studied ONeMg nova, V1974 Cygni (Nova Cygni 1992), in particular to the spectral development through the start

Robin L. Fingerhut, Marshall L. McCall, Michael De Robertis, Robin L. Kingsburgh

We have obtained low- and high-resolution spectra of the core of the highly-reddened elliptical galaxy Maffei 1. From these data, we have obtained the first measurement of the Mg2 index, and have measured the velocity dispersion and radial velocity with improved accuracy. To evaluate the extinction, a correlation between the Mg2 index and effective V-I colou

R. R. Ransom, N. Bartel, M. F. Bietenholz, M. I. Ratner

We present VLBI images of the RS CVn binary star HR 5110 (=BH CVn; HD 118216), obtained from observations made at 8.4 GHz on 1994 May 29/30 in support of the NASA/Stanford Gravity Probe B project. Our images show an emission region with a core-halo morphology. The core was 0.39 +/- 0.09 mas (FWHM) in size, or 66% +/- 20% of the 0.6 +/- 0.1 mas diameter of th

Ruth C. Peterson, Bruce W. Carney, Ben Dorman, Elizabeth M. Green

Twenty years ago, Burstein et al. (1984)suggested that strong CN and Hbeta absorption meant younger ages among globular clusters in the Andromeda galaxy (M31), unless blue stars above the main-sequence turnoff or on the horizontal branch were uncommonly prominent. Here we test these suggestions by fitting the detailed mid-ultraviolet (2280-3120A) and optical

M. Jura

The infrared excess around the white dwarf G29-38 can be explained by emission from an opaque flat ring of dust with an inner radius 0.14 of the radius of the Sun and an outer radius approximately equal to the Sun&#39;s. This ring lies within the Roche region of the white dwarf where an asteroid could have been tidally destroyed, producing a system reminisce

L. Carigi, M. Pettini

We summarise the results of recent work investigating the effects of stellar yields which take into account rotation on the predictions of chemical evolution models for early populations of galaxies.

A. P. Reynolds, J. H. J. de Bruijne, M. A. C. Perryman, A. Peacock

ESA&#39;s Superconducting Tunnel Junction (STJ) optical photon-counting camera (S-Cam2) incorporates an array of pixels with intrinsic energy sensitivity. Using the spectral fitting technique common in X-ray astronomy, we fit black bodies to nine stellar spectra, ranging from cool flare stars to hot white dwarfs. The measured temperatures are consistent with

M. Sobolewska, P. T. Zycki

We have analyzed Rossi X-ray Timing Explorer spectral data of the Galactic micro-quasar GRS 1915+105 in its various spectral states, as defined by Belloni et al. (2000). In states A and B the spectra are dominated by a strong soft thermal component, accompanied by a weak harder tail. The soft component is rather complex and cannot be described as a simple ac

Paolo Molaro

Damped Ly alpha clouds provide information on the chemistry of distant and metal poor regions of the universe. In these clouds for observational difficulties N and O are among the last elements to be measured, and C has still to be measured with precision. In combining the extant CNO abundances, we avail of a sample which includes 33 N measurements or signif

E. Rokaki, A. Lawrence, F. Economou, A. Mastichiadis

We present a new evidence of the accretion disc in active galactic nuclei, by examining the properties of the Ha emission line versus viewing angle, in a sample of superluminal (SL) quasars. Both line velocity width (FWHM) and rest equivalent width (EW) correlate with viewing angle. These correlations are quantitatively consistent with a disc geometry for bo

Naohito Nakasato, Ken&#39;ichi Nomoto

A three-dimensional hydrodynamical N-body model for the formation of the Galaxy is presented with special attention to the formation of the bulge component. Starting with cosmologically motivated initial conditions, we obtain a qualitatively similar stellar system to the Galaxy. Then we analyze the chemical and kinematic properties of the bulge stars in our

Tommy Wiklind

A method for using the sub-millimeter band to determine photometric redshifts of luminous high-z dusty galaxies is presented. It is based on the observation that local ultra-luminous IR galaxies show an average spectral energy distribution which has a remarkably small dispersion for wavelengths >50 microns. The shape of the long wavelength part is independen

Koray Karaca, Selcuk Bayin

In the light of recent observations which point to an open universe $(Ω_{0}<1)$, we construct an open singularity-free cosmological model by reconsidering a model originally constructed for a closed universe. Our model starts from a nonsingular state called prematter, governed by an inflationary equation of state $P=(γ_{p}-1)ρ$ where $γ_{p}$ $(\simeq 10^{-3}

Jun-ichi Nakashima, Shuji Deguchi

We present the results of an SiO maser survey for color-selected IRAS sources in the area 40 < l < 70 and |b| < 10 in the SiO J=1-0, v=1 and 2 transitions. We detected 134 out of 272 observed sources in SiO masers; 127 were new detections. A systematic difference in the detection rates between SiO and OH maser searches was found. Especially, in the color ran

Masato Ito

We calculate the Casimir energies due to matter fields with various boundary conditions along two compact directions in $T^{2}$ compactification. We discuss whether the Casimir energies generate attractive or repulsive forces. On the theories with extra dimensions, the Casimir energy plays a crucial role in the mechanism for stabilizing the size of extra dim

Thomas D. Cohen, Richard F. Lebed

We show that excited baryons in large N_c QCD form multiplets, within which masses are first split at O(1/N_c). The dominant couplings of resonances to various mesons are highly constrained: The N(1535) decays at leading 1/N_c order exclusively to eta-N rather than pi-N, and vice versa for the N(1650). This multiplet structure is reproduced by a simple large

R. Aleksan, P. -F. Giraud, V. Morénas, O. Pène

We try a global fit of the experimental branching ratios and CP-asymmetries of the charmless $B\to PV$ decays according to QCD factorisation. We find it impossible to reach a satisfactory agreement, the confidence level (CL) of the best fit is smaller than .1 %. The main reason for this failure is the difficulty to accomodate several large experimental branc

K. Khodjasteh, D. A. Lidar

A new method for quantum computation in the presence of detected spontaneous emission is proposed. The method combines strong and fast (dynamical decoupling) pulses and a quantum error correcting code that encodes $n$ logical qubits into only $n+1$ physical qubits. Universal fault-tolerant quantum computation is shown to be possible in this scheme using Hami

Susumu Inoue, Nobuyuki Iwamoto, Manabu Orito, Mariko Terasawa

Robust generation of gamma-ray bursts (GRBs) implies the formation of outflows with very low baryon loads and highly relativistic velocities, but more baryon-rich, slower outflows are also likely to occur in most GRB central engine scenarios, either as ``circum-jet winds&#39;&#39; or ``failed GRBs&#39;&#39;. Here we study the possibility of nucleosynthesis w

Damir Becirevic, Vittorio Lubicz, Federico Mescia, Cecilia Tarantino

We present results for the coupling of the light vector mesons to the tensor current, relative to the standard vector meson decay constants. From an O(a)-improved lattice study, performed at three values of the lattice spacing in the quenched approximation, our final values (in the continuum limit), in the MS-scheme at 2 GeV, are: (f^T/f)_rho =0.72(2)(+2/-0)